MODERN EFFORTS TO MITIGATE LAHAR HAZARDS FROM CASCADES VOLCANOES

Large lahars pose the greatest volcanic threat to communities downstream of Cascade arc volcanoes. At Mount Rainier, Washington, for example, lahars that reached the Puget lowlands have occurred repeatedly over millennia both with and without eruption. Future such flows will significantly affect highly populated areas. Effective volcano crisis management that minimizes loss of life in communities at risk relies on five key pillars: a robust monitoring network; correct data interpretation; actionable forecasts; functioning partnerships between scientists and emergency managers; and an educated and prepared at-risk populace. At Mount Rainier, the U.S. Geological Survey Cascades Volcano Observatory (CVO) has built and maintains an extensive volcano monitoring network and a lahar detection system. The lahar detection system is designed to provide earliest feasible notice of large lahars sweeping down valleys where large communities at risk could be affected within as little as an hour of event onset and smaller, closer communities within shorter timeframes. It integrates seismometers, infrasound sensors, tripwires, and cameras into a comprehensive detection network. Scientists are exploring methods for developing automated, robust, event-detection algorithms that can swiftly notify emergency management authorities, providing them maximum possible time to alert communities at risk. CVO is also engaged in active community education and outreach and working with stakeholders to periodically test alert notification procedures. To aid with interpretations of the real-time data from the network, recent modeling studies have assessed the behavior, speed, arrival times and flow depths of hypothetical lahars that originate as large landslides, providing authorities with actionable information on potential hazards faced by their communities. Volcanic hazard mitigation strategies are also being applied at other Cascade volcanoes. Combining extensive research on volcano histories and processes, establishing an extensive monitoring network, and engaging in substantial outreach and educational activities will lead to more resilient communities in high hazard areas.